The drill has been called 2-4-2 forever. I prefer to think of it as the 2-0-2 drill because when my skis are flat I don't feel the edges, as you point out. In the snow you should see a point where the edges change and there should be a gap where the ski ran flat for a moment. The longer that gap, the faster you were going, or the more disciplined you were when changing edges. The normal emphasis on the 2-4-2 drill is slow the transition down to really "feel" it. You would also ideally see the edge change occurring in the middle of your corridor. IE you travel an equal distance in transition on the old edges AND the new edges before rolling into the fall line. This takes discipline, but really allows you to develop pressure very early in the top of the turn.